Liquid metal micro switches (LIMMS) have been made that use a liquid metal, such as mercury, gallium-bearing alloys or other liquid metal composites, as the switching fluid. The liquid metal may make, break or latch electrical contacts. To change the state of the switch, a force is applied to the switching fluid, which causes it to change form and move. Liquid metal switches rely on the cleanness of the liquid metal for good performance. If the liquid metal forms oxide films or other types of corrosion product buildup within the switch, the proper functioning or performance of the switch may degrade or be inhibited.
For example, the oxide film or other corrosion products may increase the surface tension of the liquid metal, which may increase the energy required for the switch to change state over time. Films of oxide and other corrosion product may increase the tendency for the liquid metal to wet to the substrate between switch contacts, thereby increasing undesirable short circuits in the switching operation. Build up of oxide and other corrosion product may also degrade the ability of the liquid metal to wet to the switch contacts, and thereby may increase the probability of undesirable open circuits in the switching operation.
The build up of oxide and other corrosion products within the liquid metal switch may also alter the effective surface tension of the liquid metal with itself, causing the liquid metal to become stringy when moved or stretched, and thereby decreasing the tendency of the liquid metal to break cleanly between switch contacts and potentially causing short circuits and increasing the energy requirement for the switch to change state.
These issues are especially problematic for switches that are physically small, as the actuator size and strength is proportionally decreased and the surface tension forces become relatively large. This is true particularly for switches that are actuated by changes in internal pressure, but also for switches that are actuated in other ways. It is desirable to have liquid metal that is as free of corrosion products as practically possible in order to minimize these effects. Keeping other surfaces within a switch free of corrosion products is also important for good functioning, such as the switch contacts and metallic sealing surfaces to which the liquid metal wets.
It is desirable to have liquid metal that is as free of oxide and other corrosion products as practically possible in order to minimize the abovementioned negative effects. There is a need for a method to decrease or eliminate the build up of oxide or other corrosion products in liquid metal switches.
In one embodiment, a method for reducing oxides and other corrosion products on a switching fluid is disclosed. The method includes depositing a switching fluid on a first substrate. The first substrate is mated to a second substrate, the first substrate and the second substrate defining therebetween a cavity holding the switching fluid. The cavity is sized to allow movement of the switching fluid between first and second states. A gettering agent is deposited in the cavity and may prevent oxide and corrosion products from forming by reacting with free oxygen, water vapor, and other corrosive gases in the cavity.